Lens drive control device and image pickup apparatus having the same

ABSTRACT

A lens drive control device includes a zoom lens, a drive mechanism for driving at least one lens unit which constitutes the zoom lens, a control circuit for controlling the drive mechanism, and a switch for switching between a shooting state and a non-shooting state of the zoom lens, wherein, when the zoom lens is switched from the non-shooting state to the shooting state by the switch, the control circuit causes the drive mechanism to drive the zoom lens to a zoom position other than a wide-angle end.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/061,432,filed Apr. 17, 1998, now U.S. Pat. No. 6,208,472.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens drive control device and animage pickup apparatus using the lens drive control device and, moreparticularly, to a lens drive control device and an image pickupapparatus suited for use in small-sized electronic still cameras (e.g.,digital cameras) having an image pickup element such as a CCD(charge-coupled device).

2. Description of Related Art

In recent years, the image pickup apparatus using an image pickupelement such as a CCD have been widespread in the form of video camerasor electronic still cameras. These image pickup apparatus are capable oftaking and storing a video image with ease. The stored video image canbe viewed on the CRT (cathode-ray tube) or like display device orprinted out as photographs.

However, the conventional video camera and electronic still camera trendis to take over the system of the silver-halide film camera without anyconsiderable alteration. For the electronic still camera, somedisadvantages arise in employing all the features of that system.

For example, lens drive systems which prevail in the lens-shutter-typesilver-halide cameras have a common feature that, when switched from thenon-shooting mode where the lens barrel is retracted into the camerabody to the shooting mode, the zoom lens is driven to the wide-angle endin response to turning-on of the electric power supply. On the contrary,for the small-sized electronic still camera, there are occasions thatsuch an initial setting is unfavorable.

An appropriate type of optical system to the small-sized electronicstill camera is the negative lead type of zoom lens in which the frontlens unit is negative in refractive power and the rear lens unit ispositive in refractive power. In some cases, the physical length for thewide-angle end of the negative lead type of zoom lens becomes longerthan for the telephoto end. With the zoom lens of such a form, when theelectric power supply is turned on, it results that the initial settingprocess of the zoom lens goes to the wide-angle end after having oncepassed across the telephoto end. On the contrary, the electronic stillcamera has a feature that the telephoto end is rather more often enjoyedthan the wide-angle end. This is because, when the electronic stillcamera is used as a document camera to read documents into the computeror to shoot personal name cards, the telephoto end is usually used atwhich the distortion is lesser than at the wide-angle end.

On consideration of such a usage of the electronic still camera, it isnot always necessary to take the initial setting in the wide-angle endin response to turning-on of the power supply. Also, in the lensconfiguration described above, the initial setting process overruns thetelephoto end which is rather high in the frequency of use. Therefore,the zoom lens is apt to be driven wastefully, thereby causing thepremature consumption of the battery.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a lens drive controldevice which prevents the lens from being driven wastefully when theelectric power supply is turned on, and an image pickup apparatus usingthe lens drive control device.

To attain the above object, in accordance with an aspect of theinvention, there is provided a lens drive control device, whichcomprises a zoom lens, drive means for driving at least one lens unitwhich constitutes the zoom lens, control means for controlling the drivemeans, and a switch for switching between a shooting state and anon-shooting state of the zoom lens, wherein, when the zoom lens isswitched from the non-shooting state to the shooting state by theswitch, the control means causes the drive means to drive the zoom lensto a zoom position other than a wide-angle end.

In accordance with another aspect of the invention, there is provided alens drive control device, which comprises a zoom lens in which adistance between a lens surface closest to an object side and a lenssurface closest to an image side becomes minimum in a predetermined zoomposition other than a wide-angle end, drive means for driving at leastone lens unit which constitutes the zoom lens, control means forcontrolling the drive means, and a switch for switching between ashooting state and a non-shooting state of the zoom lens, wherein, whenthe zoom lens is switched from the non-shooting state to the shootingstate by the switch, the control means causes the drive means to drivethe zoom lens to the predetermined zoom position.

In accordance with a further aspect of the invention, there is provideda lens drive control device, which comprises a zoom lens, drive meansfor driving at least one lens unit which constitutes the zoom lens,control means for controlling the drive means, a switch for switchingbetween a shooting state and a non-shooting state of the zoom lens,storage means for storing a zoom position taken when the zoom lens hasbeen switched from the shooting state to the non-shooting state by theswitch, and command means for issuing a command to read out the zoomposition stored in the storage means, wherein, when the zoom lens isswitched from the non-shooting state to the shooting state by theswitch, if the command to read out the zoom position stored in thestorage means is issued by the command means, the control means causesthe drive means to drive the zoom lens to the zoom position stored inthe storage means.

In accordance with a still further aspect of the invention, there isprovided an image pickup apparatus having the lens drive control devicedescribed above.

These and further aspects and features of the invention will becomeapparent from the following description of preferred embodiments thereoftaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a block diagram of an image pickup apparatus having a lensdrive control device according to an embodiment of the invention.

FIG. 2 is a flow chart for explaining an operation of the image pickupapparatus.

FIG. 3 is a flow chart for explaining the operation of the image pickupapparatus.

FIG. 4 is a sectional side view of a lens part of the image pickupapparatus.

FIG. 5 is a front view of the lens part of the image pickup apparatus.

FIG. 6 is a diagram showing the zooming movements of lens units of anumerical example 1 of an optical system in the embodiment of theinvention.

FIGS. 7(A), 7(B) and 7(C) are longitudinal section views of thenumerical example 1 of the optical system in three operative positions.

FIGS. 8(1), 8(2), 8(3) and 8(4) are graphic representations of theaberrations of the numerical example 1 of the optical system in thewide-angle end.

FIGS. 9(1), 9(2), 9(3) and 9(4) are graphic representations of theaberrations of the numerical example 1 of the optical system in a middlefocal length position.

FIGS. 10(1), 10(2), 10(3) and 10(4) are graphic representations of theaberrations of the numerical example 1 of the optical system in thetelephoto end.

FIG. 11 is a diagram showing the zooming movements of lens units of anumerical example 2 of an optical system in the embodiment of theinvention.

FIGS. 12(A), 12(B) and 12(C) are longitudinal section views of thenumerical example 2 of the optical system in three operative positions.

FIGS. 13(1), 13(2), 13(3) and 13(4) are graphic representations of theaberrations of the numerical example 2 of the optical system in thewide-angle end.

FIGS. 14(1), 14(2), 14(3) and 14(4) are graphic representations of theaberrations of the numerical example 2 of the optical system in a middlefocal length position.

FIGS. 15(1), 15(2), 15(3) and 15(4) are graphic representations of theaberrations of the numerical example 2 of the optical system in thetelephoto end.

FIG. 16 is a diagram showing the zooming movements of lens units of anumerical example 3 of an optical system in the embodiment of theinvention.

FIGS. 17(A), 17(B) and 17(C) are longitudinal section views of thenumerical example 3 of the optical system in three operative positions.

FIGS. 18(1), 18(2), 18(3) and 18(4) are graphic representations of theaberrations of the numerical example 3 of the optical system in thewide-angle end.

FIGS. 19(1), 19(2), 19(3) and 19(4) are graphic representations of theaberrations of the numerical example 3 of the optical system in a middlefocal length position.

FIGS. 20(1), 20(2), 20(3) and 20(4) are graphic representations of theaberrations of the numerical example 3 of the optical system in thetelephoto end.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, preferred embodiments of the invention will be described indetail with reference to the drawings.

FIG. 1 is a block diagram showing an image pickup apparatus having alens drive control device according to an embodiment of the invention.

Referring to FIG. 1, a first lens unit 1 has a negative refractivepower. A second lens unit 2 has a positive refractive power. The firstlens unit 1 acts as the compensator, while the second lens unit 2 actsas the variator. The first and second lens units 1 and 2 constitute azoom lens. Incidentally, for the zoom lens configuration, many othertypes may be considered. So, it is to be understood that the zoom lensin the invention is not confined to the type shown in FIG. 1.

A stop SP, an optical low-pass filter 3 and an image sensor 4 such asinterline-type CCD are included in the optical system. Light enteringthrough the first lens unit 1 is adjusted in the intensity by the stopSP and passes through the second lens unit 2 and the low-pass filter 3to form an image on the image sensor 4.

An amplifier 5 amplifies an output signal of the image sensor 4 andoutputs the amplified output signal. A camera processing circuit 6processes the output signal of the amplifier 5 as a video signal. Thevideo signal outputted from the camera processing circuit 6 is suppliedto a recording part 7, where the video signal is recorded on a recordingmedium. As the recording medium, a magnetic disc, a magnetic tape, a PCcard, or a magneto-optical disc may be considered.

An electric motor 8 drives the stop SP, and is controlled by a CPU 14.An auto-focus (AF) circuit 9 determines a focusing state of the zoomlens at the present time on the basis of the video signal from thecamera processing circuit 6 and outputs information on the focusingstate to the CPU 14. In the image pickup apparatus in the presentembodiment, the AF method to be used is assumed to take it as thein-focus position when a frequency component of the luminance componentof the video signal reaches a peak, or the so-called the “TV signal” AF.Instead of this, the TCL type, or the infrared type may be used.

A focusing lens is driven to axially move in such a way as to makeminute excursions on the basis of the information on the focusing statesent from the AF circuit 9. In the case of the embodiment, the focusinglens may be either the first lens unit 1 or the second lens unit 2.Otherwise, both of the lens units 1 and 2 may be used as the focusinglens. As the focusing lens is driven to minutely oscillate, theluminance signal of video signal obtained by the image sensor 4oscillates in sysnchronism with the oscillation of the focusing lens.Such a luminance signal is transferred from the image sensor 4 throughthe camera processing circuit 6 and the AF circuit 9 to the CPU 14. Whenthe luminance signal exceeds a certain value, the CPU 14 determines thatan in-focus state has been attained and, then, stops the focusing lensfrom further excursion.

A reset switch 10 is provided for the first lens unit 1. When a counterdisposed in the CPU 14 is used to measure the moving amount of the firstlens unit 1, the reset switch 10 functions as a sensor for the referenceposition. Another reset switch 11 is provided for the second lens unit2. When another counter disposed in the CPU 14 is used to measure themoving amount of the second lens unit 2, the reset switch 11 functionsas a sensor for the reference position.

Stepping motors 12 and 13 function as drive means for moving the lensunits 1 and 2, respectively. When the lens units 1 and 2 are moved toeffect zooming, focusing, or retracting, the stepping motors 12 and 13are energized through respective drivers 20 and 21.

The CPU 14 functions as a control means, and, in response to therespective input signals, controls the movements of the motor 8 for thestop SP, the stepping motors 12 and 13, an electronic shutter, andothers. A trigger switch 15, when pushed, renders the CPU 14 to actuatethe electronic shutter and the recording part 7 so that the video imageformed on the image sensor 4 is taken in and recorded on the recordingmedium. A memory 16 temporarily stores information on the zoom positiontaken when the electric power supply is turned off.

A power supply switch 17, when closed, connects the electric powersupply to the CPU 14. A zoom switch 18, when pushed to the wide-angleend, actuates the CPU 14 to command the drivers 20 and 21 so thatzooming goes to the wide-angle end, or when pushed to the telephotoside, zooming goes to the telephoto side, or when not pushed, zoomingdoes not take place.

A recovery switch 19 determines which zoom position is resumed as thezoom lens moves when the power supply switch 17 is turned on again,depending on its ON/OFF position. In the present embodiment, if therecovery switch 19 is in the ON position, setting is carried out so thatthe zoom lens is driven to the position stored in the memory 16 obtainedwhen the power supply has been last turned off. If the recovery switch19 is in the OFF position, the zoom lens is driven to a position wherethe overall lens length (distance from a lens surface closest to theobject side to a lens surface closest to the image side) of the zoomlens becomes shortest.

Next, an operation of the image pickup apparatus according to theembodiment is described with reference to flow charts shown in FIGS. 2and 3.

After the flow of operation has started at a step F10, the ON/OFF of thepower supply switch 17 is first determined. If the power supply switch17 is in the on-state, the flow proceeds to a step F12, where the ON/OFFof the recovery switch 19 is determined.

If the recovery switch 19 is in the off-state, the flow proceeds to astep F13, where the lens units 1 and 2 are driven from the retractedposition (stowage position) to the zoom positions where the overall lenslength becomes shortest. Meanwhile, if the recovery switch 19 is in theon-state, the memory 19 is accessed at a step F14 to read out the zoomposition stored. Then, at a step F15, the lens units 1 and 2 are drivento the read-out zoom position.

If the zoom switch 18 is found to be turned on (to either one of thewide-angle and telephoto sides) at a step F16, the flow proceeds to astep F17, where the lens units 1 and 2 are driven along their respectiveloci toward the wide-angle end or the telephoto end depending on theswitched side of the zoom switch 18. If the zoom switch 18 is found tobe turned off, the flow proceeds to a step F18, skipping the step F17.

If, at the step F18, the trigger switch 15 is found to be turned on, theflow proceeds to a step F19, where the AF circuit 9 is driven to effectautomatic focusing. If, at a step F20, an in-focus state is found to beattained, the flow proceeds to a step F21, where the video image istaken in. At the next step F22, the recording part 17 carries outrecording of the video image on the recording medium. If the triggerswitch 15 is found to be turned off, the flow returns to the step F16.

A step F23, a check is made to find the ON/OFF of the power supplyswitch 17. If the power supply switch 17 is found to be turned on, theflow returns to the step F16. If the power supply switch 17 is found tobe turned off, the flow proceeds to a step F24, where the current zoomposition is stored in the memory 16. At the next step F25, the lensunits 1 and 2 are driven to the position where the overall lens lengthbecomes shortest. Then, at a step F26, the zoom lens is stowed(retracted) into the camera body. Then, the power supply is turned offat a step F27.

Next, with reference to FIGS. 4 and 5, the structural arrangement of alens part of the image pickup apparatus in the present embodiment isdescribed below. FIG. 4 is a longitudinal side section view of the lenspart and FIG. 4 is a front end view of the same.

In FIGS. 4 and 5, an axially movable first lens unit 101, an axiallymovable diaphragm unit 102 and an axially movable second lens unit 103correspond to the first lens unit 1, the stop SP and the second lensunit 2, respectively, shown in FIG. 1. A holding frame 104 holds thefirst lens unit 101. As the holding frame 104 moves axially, the holdingframe 104 is restrained from rotation by a guide bar 105. The guide bar105 has such a stroke as to cause the overall lens length of the zoomlens to become shorter in the non-shooting state than in the shootingstate. Another guide bar 106 guides the diaphragm unit 102 to move alongthe optical axis, and has such a stroke as to cause the overall lenslength of the zoom lens to become shorter in the non-shooting state thanin the shooting state. A holding frame 107 holds the second lens unit103. As the holding frame 107 moves axially, the holding frame 107 i srestrained from rotation by a guide bar 108. The guide bar 105 has sucha stroke as to cause the overall lens length of the zoom lens to becomeshorter in the non-shooting state than in the shooting state. A U bar109 restrains the first holding frame 104, the diaphragm unit 102 andthe second holding frame 107 from turning about the respective guidebars 105, 106 and 108 in the direction perpendicular to the opticalaxis, and has such a stroke as to cause the overall lens length of thezoom lens to become shorter in the non-shooting state than in theshooting state.

A stepping motor 110 is arranged to drive the holding frame 104 axially.A rack 111 transmits the driving force of the stepping motor 110 to theholding frame 104. A sensor 112 is arranged to detect the initialposition of the first lens unit 101. Another stepping motor 113 isarranged to drive the second lens unit 103 axially. Another rack 114transmits the driving force of the stepping motor 113 to the holdingframe 107. Another sensor 115 is arranged to detect the initial positionof the second lens unit 103. The stepping motors 110 and 113 correspondto the stepping motors 12 and 13 shown in FIG. 1, respectively, and thesensors 112 and 115 correspond to the reset switches 10 and 11 shown inFIG. 1, respectively.

A spring 116 urges the diaphragm unit 102 always toward the object side.A main tube 117 holds the guide bars 105, 106 and 108 and the bar 109 attheir one ends, and fixedly carries the stepping motors 110 and 113 andthe sensors 112 and 115.

A CCD unit 118 is integrally composed of a low-pass filter 118 a and achip 118 c and has an image receiving surface 118 b. The CCD unit 118corresponds to a combination of the low-pass filter 3 and the imagesensor 4 shown in FIG. 1.

A rear tube 119 holds the guide bars 105, 106 and 108 and the U bar 109at their opposite ends and fixedly carries the CCD unit 118. Thestepping motors 110 and 113 are mounted on a motor holding plate 120.

The upper half of FIG. 4 shows the state of the lens part in which thefirst lens unit 101 is in the most forward position. The lower half ofFIG. 4 shows the state in which the lens part is in the retractedposition. In moving the first lens unit 101 forward, the stepping motor110 is energized to transmit its driving force to the rack 111. Thedriving force transmitted to the rack 111 causes the holding frame 104to axially move forward. Along with the forward movement of the holdingframe 111, the diaphragm unit 102 which is urged by the spring 116toward the object side, too, is moved forward. The diaphragm unit 102,which is being moved forward, eventually abuts on a stopper 117 aprovided on the main tube 117 and stops from further moving forward,thus reaching the position of the upper half of FIG. 4. On the otherhand, in moving the first lens unit 101 backward, the stepping motor 110is energized in the reversed direction. So, the reverse driving force ofthe stepping motor 110 is transmitted to the rack 111 to move theholding frame 104 toward the image side. After a projection 104 a of theholding frame 104, which is being moved backward, abuts on the diaphragmunit 102, the diaphragm unit 102, too, is moved backward together withthe holding frame 104, thus reaching the position of the lower half ofFIG. 4.

The driving force generated by the stepping motor 113 is transmittedthrough the rack 114 to the holding frame 107, thus axially moving theholding frame 107 backward and forward. The sensor 112 is arranged todetect the initial position of the holding frame 104 and the sensor 115is arranged to detect the initial position of the holding frame 107. Thesensors 112 and 115 send detection signals to a CPU (not shown in FIGS.4 and 5), which corresponds to the CPU 14 shown in FIG. 1. The CPUcontrols the energization of the stepping motors 110 and 113 inaccordance with the detection signals received.

Next, numerical examples 1 to 3 of optical systems suited for use in thelens drive control device in the present embodiment are shown. In thenumerical data for the examples 1 to 3, ri is the radius of curvature ofthe i-th lens surface, when counted from the object side, di is the i-thlens thickness or air separation, when counted from the object side, niis the refractive index of the material of the i-th lens element, whencounted from the object side, and νi is the Abbe number of the materialof the i-th lens element, when counted from the object side. The lenssurface indicated by * is an aspheric surface, and in the numerical datathere are also the values of the radius of the osculating sphere and theaspheric coefficients in the following polynomial:$X = {\frac{h^{2}/R}{1 + \sqrt{1 - {\left( {1 + K} \right)\left( {h/R} \right)^{2}}}} + {Bh}^{4} + {Ch}^{6} + {Dh}^{8}}$

where X is the coordinate in the direction of the optical axis and h isthe coordinate in the direction perpendicular to the optical axis, thedirection in which light advances being taken as positive. R is theradius of the osculating sphere, and K, B, C and D are the asphericcoefficients. Also, the notation D-0X means 10^(−x).

Numerical Example 1: f = 3.74849 Fno = 1:2.8 2ω = 64.8°  r 1 = 205.814 d1 = 1.00 n 1 = 1.74330 ν 1 = 49.2 *r 2 = 3.621 d 2 = 1.35  r 3 = 6.370 d3 = 2.10 n 2 = 1.64769 ν 2 = 33.8  r 4 = 46.696 d 4 = Variable  r 5 =∞(Stop) d 5 = Variable  r 6 = 4.880 d 6 = 2.20 n 3 = 1.83400 ν 3 = 37.2 r 7 = −76.972 d 7 = 0.18  r 8 = −20.357 d 8 = 1.60 n 4 = 1.84666 ν 4 =23.8  r 9 = 3.588 d 9 = 0.11  r10 = 3.929 d10 = 1.90 n 5 = 1.73077 ν 5 =40.6 *r11 = −84.003 d11 = Variable  r12 = ∞ d12 = 3.10 n 6 = 1.51633 ν 6= 64.2  r13 = ∞ Variable Focal Length Separation 3.75 8.55 11.02 d 411.74 2.17 1.20 d 5 6.69 2.61 1.20 d11 2.00 5.62 7.49 AsphericCoefficients: For r 2: R = 3.62053D + 00 K = −1.06318D + 00 B = 1.10799D− 03 C = −3.27073D − 06 For r11: R = −8.40029D + 01 K =−2.06156D + 02 B= 2.51718D − 03 C = 1.50000D − 04

Numerical Example 2: f = 3.75003 Fno = 1:2.8 2ω= 63.6°  r 1 = 60.170 d 1= 1.00 n 1 = 1.74330 ν = 49.2 *r 2 = 3.472 d 2 = 2.78  r 3 = 8.363 d 3 =4.13 n 2 = 1.84666 ν 2 = 23.8  r 4 = 17.062 d 4 = Variable  r 5 =∞(Stop) d 5 = 1.10  r 6 = 6.211 d 6 = 4.78 n 3 = 1.69680 ν 3 = 55.5  r 7= −10.395 d 7 = 0.31  r 8 = −6.817 d 8 = 2.00 n 4 = 1.84666 ν 4 = 23.8 r 9 = −2163.195 d 9 = 1.20  r10 = 10.043 d10 = 1.60 n 5 = 1.73077 ν 5 =40.6 *r11 = 21.256 d11 = Variable  r12 = 154.453 d12 = 1.00 n 6 =1.80400 ν 6 = 46.6  r13 = −23.948 d13 = 3.10  r14 = ∞ d14 = 3.10 n 7 =1.51633 ν 7 = 64.2  r15 = ∞ Variable Focal Length Separation 3.75 8.6011.10 d 4 11.85 2.69 1.10 d11 1.12 9.04 13.12 Aspheric Coefficients: Forr 2: R = 3.47155D + 00 K = −1.52122D + 00 B = 2.11152D − 03 C =−1.34125D − 05 For r11: R = 2.12556D + 01 K = 6.49763D + 01 B = 3.59566D− 04 C = −5.36520D − 05

Numerical Example 3: f = 3.75000 Fno = 1:2.8 2ω= 64.6°  r 1 = −1580.189d 1 = 1.00 n 1 = 1.58313 ν 1 = 59.4 *r 2 = 2.786 d 2 = 1.85  r 3 = 5.844d 3 = 1.50 n 2 = 1.84666 ν 2 = 23.8  r 4 = 10.648 d 4 = Variable  r 5 =∞(Stop) d 5 = 1.10  r 6 = 5.328 d 6 = 2.10 n 3 = 1.58313 ν 3 = 59.4  r 7= −11.129 d 7 = 0.30  r 8 = −44.181 d 8 = 1.00 n 4 = 1.84666 ν 4 = 23.8 r 9 = 6.765 d 9 = 0.38 *r10 = −17.497 d10 = 1.50 n 5 = 1.80610 ν 5 =40.9  r11 = −6.978 d11 = Variable  r12 = 12.184 d12 = 1.50 n 6 = 1.51633ν 6 = 64.1  r13 = −51.853 d13 = 3.10  r14 = ∞ d14 = 3.10 n 7 = 1.51633 ν7 = 64.2  r15 = ∞ Variable Focal Length Separation 3.75 8.60 11.10 d 411.85 2.69 1.10 d11 1.12 9.04 13.12 Aspheric Coefficients: For r 2: R =2.78636D + 00 K = −6.97078D − 01 B = −4.78910D − 04 C = 1.77019D − 05 D= −1.64098D − 06 For r10: R = 5.32776D + 00 K =− 9.08473D − 01 B =−7.94778D − 04 C =− 1.82429D − 06 D = −1.44616D − 06

FIG. 6 shows the total zooming movement of each of the lens units in theparaxial zone of the numerical example 1. The optical system of thenumerical example 1 is of the 2-unit type with the minus-plus refractivepower arrangement. The negative first lens unit as the compensator andthe positive second lens unit as the variator are moved in differentialrelation to vary the focal length.

As is apparent from FIG. 6, in the numerical example 1, the overall lenslength (a distance between a lens surface closest to the object side anda lens surface closest to the image side) of the zoom lens is shortestin the telephoto end. In application of the invention to the opticalsystem of the numerical example 1, it is, therefore, desirable that theretraction starts from the telephoto end and, when the power supply isturned on, the zoom lens first moves to the telephoto end.

FIGS. 7(A), 7(B) and 7(C) are longitudinal section views of thenumerical example 1 of the optical system in three zoom positions. Theoverall lens length of the zoom lens is shortest in the telephoto end asshown in FIG. 6. FIGS. 8(1), 8(2), 8(3) and 8(4) to FIGS. 10(1), 10(2),10(3) and 10(4) are graphic representations of the aberrations of thenumerical example 1 of the optical system in the respective zoompositions indicated in FIGS. 7(A), 7(B) and 7(C). FIGS. 8(1) to 8(4) arein the wide-angle end, FIGS. 9(1) to 9(4) are in a middle focal lengthposition, and FIGS. 10(1) to 10(4) are in the telephoto end.

FIG. 11 shows the total zooming movement of each of the lens units ofthe numerical example 2. The optical system of the numerical example 2is of the 3-unit type with the minus-plus-plus refractive powerarrangement. The negative first lens unit and the positive second lensunit are moved in differential relation to vary the focal length.

As is apparent from FIG. 11, in the numerical example 2, the overalllens length of the zoom lens is shortest in a zoom position indicated byA. In application of the invention to the numerical example 2, it is,therefore, desirable that the retraction starts from the zoom positionA, and when the power supply is turned on, the zoom lens first moves tothe zoom position A.

FIGS. 12(A), 12(B) and 12(C) are longitudinal section views of thenumerical example 2 of the optical system in three zoom positions. Theoverall lens length of the zoom lens is shortest neither in thewide-angle end nor in the telephoto end, but in a certain zoom positionfor the middle focal length. FIGS. 13(1), 13(2), 13(3) and 13(4) toFIGS. 15(1), 15(2), 15(3) and 15(4) are graphic representations of theaberrations in the respective zoom positions shown in FIGS. 12(A), 12(B)and 12(C). FIGS. 13(1) to 13(4) are in the wide-angle end, FIGS. 14(1)to 14(4) are in the middle focal length position, and FIGS. 15(1) to15(4) are in the telephoto end.

FIG. 16 shows the total zooming movement of each of the lens units ofthe numerical example 3. The optical system of the numerical example 3is of the 3-unit type with the minus-plus-plus refractive powerarrangement. The negative first lens unit and the positive second lensunit are moved in differential relation to vary the focal length.

As is apparent from FIG. 16, in the numerical example 3, the overalllens length of the zoom lens is shortest in a zoom position indicated byB. In application of the invention to the numerical example 3, it is,therefore, desirable that the retraction starts from the zoom positionB, and when the power supply is turned on, the zoom lens first moves tothe zoom position B.

FIGS. 17(A), 17(B) and 17(C) are longitudinal section views of thenumerical example 3 of the optical system in three zoom positions. Theoverall lens length of the zoom lens is shortest neither in thewide-angle end nor in the telephoto end, but in a certain zoom positionfor the middle focal length. FIGS. 18(1), 18(2), 18(3) and 18(4) toFIGS. 20(1), 20(2), 20(3) and 20(4) are graphic representations of theaberrations in the respective zoom positions indicated by FIGS. 17(A),17(B) and 17(C). FIGS. 18(1) to 18(4) are in the wide-angle end, FIGS.19(1) to 19(4) are in a middle focal length position, and FIGS. 20(1) to20(4) are in the telephoto end.

The image pickup apparatus in the present embodiment, when the powersupply is turned on, moves the lens from the retracted position to thatzoom position which compromises the minimum distance and the highfrequency of use. Therefore, the shooting state can be quickly made up.Also, since the zoom position taken when the power supply has beenturned off at the last time is stored, the zoom lens can be moved to thestored zoom position, if necessary, when the power supply is turned onagain. Therefore, the wasteful driving of the zoom lens can be reduced.So, the consumption of the battery in the image pickup apparatus can bereduced.

As has been described above, in the lens drive control device and theimage pickup apparatus according to the embodiment of the invention, thewasteful lens driving can be reduced when the power supply is turned on.

What is claimed is:
 1. An optical appliance, comprising: a zoom lenshaving a first lens unit of negative refractive power located closest toan object side which moves including a locus convex toward an image sideduring zooming from a wide angle end to a telephoto end; an actuatorwhich moves the lens unit of the zoom lens; a switch which switchesbetween a retracted state and a non-retracted state of the zoom lens;and a controller which controls the actuator to move the lens unit ofthe zoom lens to a position other than the wide angle end when the zoomlens is switched from the retracted state to the non-retracted state bythe switch.
 2. An optical appliance according to claim 1, wherein thezoom lens has in the order from the object side to the image side afirst lens unit of negative refractive power and a second lens unit ofpositive refractive power.
 3. An optical appliance according to claim 1,wherein the zoom lens has in the order from the object side to the imageside a first lens unit of negative refractive power, a second lens unitof positive refractive power and a third lens unit of positiverefractive power.
 4. An optical appliance according to claim 1, whereinthe controller controls the actuator to move the lens unit of the zoomlens to a predetermined zoom position at which the first lens unit ispositioned closest to the image side.
 5. An optical appliance,comprising: a zoom lens having a plurality of lens units, a lens unitclosest to an object side of the plurality of lens units beingpositioned closest to an image side at a predetermined zoom positionother than a wide angle end; an actuator which moves the lens unit ofthe zoom lens; a switch which switches between a retracted state and anon-retracted state of the zoom lens; and a controller which controlsthe actuator to move the lens unit of the zoom lens to a position otherthan a wide angle end, when the zoom lens is switched from the retractedstate to the non-retracted state by the switch.
 6. An optical applianceaccording to claim 5, wherein the zoom lens have in the order from theobject side to the image side a first lens unit of negative lens unitand a second lens unit of positive refractive power.
 7. An opticalappliance according to claim 5, wherein the zoom lens has in the orderfrom the object side to the image side a first lens unit of negativerefractive power, a second lens unit of positive power, and a third lensunit of positive power.
 8. An optical appliance according to claim 5,wherein the controller controls the actuator to move the lens unit ofthe zoom lens to a predetermined zoom position at which the lens unitclosest to the object side is positioned closest to the image side.